The present invention relates to a device and a method, as well as to a network architecture, for redirecting traffic within a mobile telephone network.
Many mobile telephone networks currently offer roaming services, allowing users who have subscribed to the service to continue to receive telephone services during trips abroad. In this way, the user can use any mobile telephone network with no specific criteria in terms of prices or better links, and to do so in an entirely random manner. For commercial reasons, certain operators have set up devices and methods for redirecting traffic in order to favour the tracking of their roaming subscribers in a given country, so that they are led to use the services provided by one operator over another.
In this regard, the prior art knows a device such as described in patent application EP1463366 relating to a roaming service, which is part of a mobile telephone network comprising an HPLMN or Home Public Land Mobile Network, and a VPLMN or Visited Public Land Mobile Network, both of which are connected by an SS7 transport network, which is a Code 7 semaphore signalling network. This HPLMN network comprises a preference unit. This preference unit probes data exchanges between the visited network and the user's home network, meaning that it filters data exchanges between an HLR, Home Location Register, which contains data relating to a customer, and an MSC/VLR, which is a switching device containing the data of the user within its coverage zone transmitted by the HLR. In this way, it captures a tracking request sent by the MSC/VLR from the visited network VPLMN to the HLR of the user's home network HPLMN. This preference unit comprises a database which it consults in order to check that the network is included in its list of favourite networks. If so, it transmits the captured tracking request to the HLR; if not, this preference unit will send a negative response to the tracking request to the MSC/VLR. Upon receiving this negative response, the MSC/VLR will refuse the connection to the mobile terminal, which will then try to connect to another VPLMN network. In this way, the preference unit will therefore redirect the traffic and can send a positive message to the MSC/VLR during another connection by the mobile terminal to a VPLMN network referenced as a partner by this preference unit, even when no roaming agreement has been signed. The disadvantage of such a device is that it cannot redirect traffic if an interoperability problem exists between the VPLMN and HPLMN networks, since in such a context the preference unit, device which manages the redirection of traffic, is no longer in contact with the visited network.
The present invention aims to solve the disadvantages of the prior art. One aim of the invention is to guarantee continuity of service to a mobile terminal, even in the event of interoperability problems between the HPLMN and VPLMN networks. For this purpose, the present invention relates initially to a mobile telephone network architecture comprising at least one first home network and a second visited network, said visited network comprising at least one visited switching device, said home network comprising at least one home switching device, said visited switching device being capable of receiving data relating to a user in said visited network and of transmitting said data to said home switching device, said home switching device being capable of recording said data and authenticating and tracking said user on the basis of said data, said architecture comprising an intermediate device positioned in said visited network, said intermediate device comprising:                reception means devised to receive said data from said visited switching device;        recording means devised to record said data;        connection request means devised to send a request to said home switching device on the basis of said data;                    connection simulation means devised to supply said visited switching device with an authorisation to connect said user to said visited network.The configuration of this network architecture offers the advantage of comprising within the visited network an intermediate device which carries all data exchanges between the switching devices of the home and visited networks. The position of this device and the means that it include allow it to guarantee continuity of service in the event of an interoperability problem.                        
The invention also relates to a method of managing a network architecture, said architecture comprising at least one first home network and a second visited network, said visited network comprising at least one visited switching device, said home network comprising at least one home switching device, said visited switching device being capable of receiving data from a user in said visited network and of transmitting said data to said home switching device, said home switching device being capable of recording said data and of authenticating and tracking said user on the basis of said data, said method comprising steps consisting of:                receiving said data from said visited switching device;        recording said data;        sending a request to said home switching device on the basis of said data;                    supplying said visited switching device with an authorisation to connect said user to said visited network.                        
In one embodiment of the invention, it includes, in the event of an authentication failure by said home switching device following said request, a step consisting of:                analysing said data received by said intermediate device;        authorising the authentication.This step allows a user of the visited network to receive mobile telephone service even when the authentication of his/her mobile terminal is not possible, for example following the non-availability of the home network switching device. In this case it is the intermediate device that authorises the authentication.        
In another embodiment of the invention, it includes, in the event of a tracking failure by said home switching device following said request, a step consisting of:                analysing said data received by said intermediate device;        authorising the tracking.This step allows a user of the visited network to receive mobile telephone service even when the tracking of his/her mobile terminal is not possible. In this case it is the intermediate device that authorises the tracking.        
The invention also relates to an intermediate device comprised within a mobile telephone network architecture including at least one first home network and a second visited network, said visited network comprising at least one visited switching device, said home network comprising at least one home switching device, said visited switching device being capable of receiving data relating to a user within said visited network and of transmitting said data to said home switching device, said home switching device being capable of recording said data and of authenticating and tracking said user on the basis of said data, intermediate device including:                reception means devised to receive said data from said visited switching device;        recording means devised to record said data;        connection request means devised to send a request to said home switching device on the basis of said data;        connection simulation means devised to supply said visited switching device with an authorisation to connect said user to said visited network.This intermediate device has the advantage, on the basis of the means it comprises, of being replaceable with the visited network switching device, but also with the home network switching device, and thus of being able to guarantee mobile telephone service in the event of an interoperability problem.        